Under the IALA cardinal system, a mark with a quick light showing 9 flashes every 15 seconds indicates that the safest water is on which side of the mark?

Correct Answer: Option A — west side of the mark

Cardinal marks use clock-face analogies for quick/very quick flashes. Nine flashes followed by a dark period represent the West cardinal mark, indicating that the safest and deepest navigable water lies on the west side.